Proton-Conductive Crystals Based on Polyoxometalates

Abstract

Polyoxometalates (POMs) are discrete metal–oxo cluster anions comprising high-valence transition metals (Mo, W, V, Nb, etc.) and have been researched in broad areas of sciences. POMs have attracted considerable attention as an important class of protonconductive materials since POMs can efficiently transport protons (H⁺) due to their small effective negative surface charge density. However, the acid salts of POMs suffer from low structural stability and practical applications are limited. A promising approach to overcome the drawback is hybridizing POMs with appropriate counter cations and/or polymers to achieve high structural stability and proton conductivity.